Quantum dots: time of growth and change: Page 3 of 6

July 27, 2018 //By Dr Khasha Ghaffarzadeh
Quantum dots: time of growth and change
Quantum dots (QDs) are no longer a young technology. Even their commercialization process is not new since the pioneering companies were formed in the 2001-2005 period. The QDs are also not commercially novice: they have been employed in LCD displays as remote phosphors for several years.  

Today, film type QDs in displays reign supreme because they keep QDs sufficiently away from sources of heat and light stress. They are however likely only a transiently solution because, as shown in our technology roadmap, improved materials will in time enable color filter QDs, on-chip QDs and finally emissive QD displays. Below, we briefly mention what is needed for each implementation.

We provide details in the report.

Color filter: QDs must be better dispersed in resins or inks and must survive the baking/curing process without too much degradation. The QDs must limit their self-absorption and boost their blue absorbance. The surrounding system must also change around them, adopting in-cell polarizers and potentially a backpass filter. Would it be worth the effort? The prize is improved efficiency, widened color gamut, and expanded viewing angle.  

On-chip: QDs must be much more tolerant of light and heat stress. This is critical and the industry is exploring many strategies such as softening the interface in the core-shell-ligand system, new inorganic protective coatings, novel ligands, and so on. Today, QDs tolerate mild conditions found in low power LEDs and some (not all) microLED applications, but going beyond that requires extensive sustained development.  

Emissive: QDs are in many ways the ultimate optical material. They give wide color gamut, high efficiency, high contrast, solution processing, and thinness (thus flexibility). They are however at an early stage of development with much scientific work still to be done. The efficiency gap with OLED, particularly for Cd free QDs, must be bridged; the lifetime must be drastically prolonged; the optimal device stack composition and geometry must be established; methods to manufacture high PPI three-color displays must be developed and scaled; and so on.

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